Image processing apparatus to estimate a plurality of road surfaces

ABSTRACT

An image processing apparatus includes one or more processors; and a memory, the memory storing instructions, which when executed by the one or more processors, cause the one or more processors to generate vertical direction distribution data indicating a frequency distribution of distance values with respect to a vertical direction of a range image, from the range image having distance values according to distance of a road surface in a plurality of captured images captured by a plurality of imaging parts; estimate a plurality of road surfaces, based on the vertical direction distribution data; and determine a desired road surface, based on the estimated plurality of road surfaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of InternationalApplication No. PCT/JP2017/002550, filed on Jan. 25, 2017, which claimspriority to Japanese Patent Application No. 2016-053383, filed on Mar.17, 2016. The contents of these applications are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The disclosures discussed herein relate to an image processingapparatus, an imaging device, a moving body device control system, animage processing method, and a program product.

2. Description of the Related Art

In vehicle safety, automobile body structures and the like have beendeveloped from the perspectives of pedestrian and passenger protectionagainst collision with pedestrians and other automobiles. Recentadvances in information processing and image processing technologieshave led to the development of high rate detection techniques fordetecting people, automobiles, etc. Automobiles applied with thesetechnologies are already on sale; such automobiles automatically applybrakes before collision in order to prevent collision.

In order to apply brakes automatically, measuring a distance between anautomobile and an object such as a person, another automobile, etc. ismandatory; hence, measurement using images of stereo cameras has beenput into practical use for that reason.

An object recognition technique for recognizing an object such as aperson or another vehicle by performing the following image processingis known in the related art, in measurement using images captured bysuch a stereo camera (see, e.g., Patent Document 1).

According to this technique, first, a V-Disparity image is generatedwith a vertical coordinate of an image as one axis, disparity of theimage as the other axis, and a value of disparity frequency as a pixelvalue, from a plurality of images captured by a stereo camera. Next, aroad surface is detected from the generated V-Disparity image. Afterremoving noise using the detected road surface, a U-Disparity image isgenerated with a horizontal coordinate of an image as a vertical axis,parallax of the image as the horizontal axis, and the disparityfrequency as the pixel value. Then, an object such as a person oranother vehicle is recognized based on the generated U-Disparity image.

However, in the related art technique, noise is generated in parallaxdue to reflection of a road surface in rainy weather and the roadsurface is unable to be accurately measured.

SUMMARY OF THE INVENTION

According to an aspect of the disclosure, an image processing apparatusincludes

one or more processors; and

a memory, the memory storing instructions, which when executed by theone or more processors, cause the one or more processors to:

generate vertical direction distribution data indicating a frequencydistribution of distance values with respect to a vertical direction ofa range image, from the range image having distance values according todistance of a road surface in a plurality of captured images captured bya plurality of imaging parts;

estimate a plurality of road surfaces, based on the vertical directiondistribution data; and

determine a desired road surface, based on the estimated plurality ofroad surfaces.

RELATED ART DOCUMENT Patent Document

-   [Patent Document 1] Japanese Unexamined Patent Application    Publication No. 2015-075800

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and further features of embodiments will be apparent fromthe following detailed description when read in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating a configuration of anin-vehicle device control system, according to an embodiment;

FIG. 2 is a schematic diagram illustrating configurations of an imagingunit and an image analysis unit, according to an embodiment;

FIG. 3 is a functional block diagram illustrating a moving body devicecontrol system, according to an embodiment;

FIG. 4A is a diagram illustrating parallax image data and a V-mapgenerated from the parallax image data;

FIG. 4B is a diagram illustrating parallax image data and a V-mapgenerated from the parallax image data;

FIG. 5A is a diagram illustrating an example of a captured image as areference image captured by one imaging part;

FIG. 5B is a diagram illustrating an example of a V-map corresponding tothe captured image of FIG. 5A;

FIG. 6A is a diagram illustrating an example of a captured image as areference image captured by one imaging part;

FIG. 6B is a diagram illustrating an example of a V-map in apredetermined region corresponding to the captured image of FIG. 6A;

FIG. 7A is a diagram illustrating an example of a captured image as areference image captured by one imaging part when noise is generated;

FIG. 7B is a diagram illustrating an example of a V-map in apredetermined region corresponding to the captured image of FIG. 7A whennoise is generated;

FIG. 8 is a functional block diagram illustrating an example of a firstroad surface estimation unit;

FIG. 9 is a flowchart illustrating an example of a sample pointextraction process;

FIG. 10 is a diagram illustrating an example of a process of extractingsample points from a first segment;

FIG. 11A is a diagram illustrating an example of a process of extractingsample points from a second segment;

FIG. 11B is a diagram illustrating an example of a process of extractingsample points from the second segment;

FIG. 12 is a diagram illustrating another example of a process ofextracting sample points from the second segment;

FIG. 13 is a flowchart illustrating an example of an outlier removalprocess;

FIG. 14 is a diagram illustrating a process of removing an outlier;

FIG. 15 is a diagram illustrating an example of a road surfaceestimation process performed by a second road surface estimation unit;

FIG. 16 is a flowchart illustrating an example of a road surfacedetermination process;

FIG. 17A is a diagram illustrating an example of the road surfacedetermination process;

FIG. 17B is a diagram illustrating an example of the road surfacedetermination process;

FIG. 18 is an example of a flowchart illustrating a road surfacedetermination process according to a second embodiment;

FIG. 19A is a diagram illustrating an example of a region such as arectangle including a first road surface and a second road surface;

FIG. 19B is a diagram illustrating an example of a region such as arectangle including the first road surface and the second road surface;

FIG. 20 is an example of a flowchart illustrating a road surfacedetermination process according to a third embodiment; and

FIG. 21 is a diagram illustrating a correspondence relationship betweenone of a captured image or a parallax image, and a V-map.

DESCRIPTION OF THE EMBODIMENTS

The following illustrates a moving body device control system having animage processing apparatus according to an embodiment.

First Embodiment

<Configuration of in-Vehicle Device Control System>

FIG. 1 is a diagram illustrating a configuration of an in-vehicle devicecontrol system acting as a moving body device control system, accordingto an embodiment of the present invention.

The in-vehicle device control system 1 is installed in a referencevehicle 100 such as an automobile that is a moving body. The in-vehicledevice control system 1 includes an imaging unit 500, an image analysisunit 600, a display monitor 103, and a vehicle traveling control unit104. The in-vehicle device control system 1 detects relative heightinformation (information indicating relative inclination condition) of aroad surface (moving body traveling surface) ahead of the referencevehicle, from image data each having an image of a forward region of themoving body in a reference vehicle traveling direction (imaging region)obtained by the imaging unit 500, detects a three-dimensional shape ofthe traveling road surface ahead of the reference vehicle from thedetection result of the relative height information, and controls themoving body and various in-vehicle devices using the detection result ofthe three-dimensional shape of the traveling road surface. The controlof the moving body includes, for example, transmission of alert signs,control of a steering wheel of the reference vehicle 100 (referencemoving body), or braking of the reference vehicle 100 (the referencemoving body).

For example, the imaging unit 500 is disposed in the vicinity of arear-view mirror (not illustrated) of a windshield 105 of the referencevehicle 100. Various data such as captured image data obtained by theimaging unit 500 are input into the image analysis unit 600 acting as animage processing unit.

The image analysis unit 600 analyzes data transmitted from the imagingunit 500, detects a relative height (positional information) at eachpoint on a road surface ahead of the reference vehicle with respect to aroad surface portion (a road surface portion directly beneath thereference vehicle) on which the reference vehicle 100 is traveling, andobtains a three-dimensional shape of the (moving body) traveling roadsurface ahead of the reference vehicle. Further, the image analysis unit600 recognizes recognition target objects such as other vehicles,pedestrians, various obstacles, etc., ahead of the reference vehicle.

The analysis results of the image analysis unit 600 are sent to thedisplay monitor 103 and the vehicle traveling control unit 104. Thedisplay monitor 103 displays captured image data obtained by the imagingunit 500 and analysis results. The vehicle traveling control unit 104may, for example, send an alert sign to a driver of the referencevehicle 100 or perform traveling support control such as control of thesteering wheel and braking of the reference vehicle, based on therecognition results of a recognition target object obtained by the imageanalysis unit 600 such as another vehicle, pedestrian, and variousobstacles ahead of the vehicle.

<Configurations of Imaging Unit 500 and Image Analysis Unit 600>

FIG. 2 is a diagram illustrating configurations of the imaging unit 500and the image analysis unit 600 according to an embodiment.

The imaging unit 500 includes a stereo camera having two imaging parts510 a and 510 b as imaging units. The two imaging parts 510 a and 510 bare the same components. The imaging parts 510 a and 510 b includeimaging lenses 511 a and 511 b, sensor substrates 514 a and 514 bincluding image sensors 513 a and 513 b having two-dimensionallyarranged light receiving elements, and signal processors 515 a and 515 bconfigured to generate and output captured image data obtained byconverting analog electric signals output from the sensor substrates 514a and 514 b (electric signals corresponding to amounts of light receivedby respective light receiving elements on the image sensors 513 a and513 b) into digital electric signals. The imaging unit 500 outputsluminance image data and parallax image data.

In addition, the imaging unit 500 includes a process hardware unit 510including a Field-Programmable Gate Array (FPGA) or the like. In orderto obtain parallax images from the luminance image data output from theimaging parts 510 a and 510 b, the process hardware unit 510 includes adisparity calculation unit 511 as a parallax image informationgeneration unit to calculate a disparity value of a corresponding imageportion between the respective captured images captured by the imagingparts 510 a and 510 b.

The disparity value referred to in this case is a value obtained bytaking one of the captured images captured by the imaging parts 510 aand 510 b as a reference image, and the other one as a comparison image,and calculating a positional deviation corresponding to a same pointwithin the imaging region of an image portion on the comparison imagewith respect to an image portion on the reference image, as a disparityvalue of the image portion. By utilizing the principle of triangulation,a distance to the same point within an imaging region corresponding tothe image portion may be calculated based on the disparity value of theimage portion.

The image analysis unit 600 is configured to include an image processingboard or the like; the image analysis unit 600 includes a storage unit601 having a RAM, a ROM or the like configured to store the luminanceimage data and the parallax image data output from the imaging unit 500,a central processing unit (CPU) 602 configured to execute a computerprogram for performing disparity calculation control and the like, adata interface (I/F) 603, and a serial I/F 604.

The FPGA constituting the process hardware unit 510 executes a processrequiring real-time processing on image data, for example, gammacorrection, distortion correction (parallelization of left and rightcaptured images), and disparity calculation by block matching togenerate parallax images and write the generated information in the RAMof the image analysis unit 600. The CPU of the image analysis unit 600is responsible for control of an image sensor control unit of each ofthe imaging parts 510 a and 510 b and overall control of the imageprocessing board. The CPU of the image analysis unit 600 also loads aprogram for executing a process of detecting a three-dimensional shapeof a road surface, a process of detecting various objects (objects) suchas guardrails, and the like from the ROM, executes various kinds ofprocesses by inputting the luminance image data and the parallax imagedata stored in the RAM, and outputs the process results to the outsidefrom the data I/F 603 and the serial I/F 604. Upon execution of suchprocesses, vehicle operation information, such as vehicle velocity andacceleration (mainly acceleration in a longitudinal direction of thevehicle), steering angle, and yaw rate of the reference vehicle 100, isinput via the data I/F 603, and used as parameters of various kinds ofprocesses. The data output to the outside may be used as input data forcontrolling the various devices of the reference vehicle 100 (brakecontrol, vehicle velocity control, warning control, etc.).

Note that the imaging unit 500 and the image analysis unit 600 mayintegrally form an imaging device 2, as an integrated device.

FIG. 3 is a functional block diagram of an in-vehicle device controlsystem 1 implemented by the process hardware unit 510, the imageanalysis unit 600, and the vehicle traveling control unit 104 in FIG. 2.Note that a functional unit implemented by the image analysis unit 600is implemented by a process executed by the CPU 602 of the imageanalysis unit 600 by one or more programs installed in the imageanalysis unit 600.

The following illustrates processes according to an embodiment.

<Parallax Image Generation Process>

A parallax image generation unit 11 performs a parallax image generationprocess for generating parallax image data (parallax image information).Note that the parallax image generation unit 11 is constituted by, forexample, a disparity calculation unit 511 (FIG. 2).

The parallax image generation process includes, first, setting theluminance image data of one imaging part 510 a of the two imaging parts510 a and 510 b as reference image data, setting the luminance imagedata of the other imaging part 510 b as comparison image data,calculating disparity between the two sets of the luminance image data,generating parallax image data based on the calculated disparity, andoutputting the generated parallax image data. The parallax image dataindicates a parallax image including respective image portions withrespective pixel values according to disparities d calculated forrespective image portions on the reference image data.

Specifically, the parallax image generation unit 11 defines a blockincluding a plurality of pixels (e.g., 16 pixels×1 pixel) having onetarget pixel in the center with respect to a certain row of thereference image data. By contrast, in the same row in the comparisonimage data, a correlation value, which indicates a correlation between afeature quantity indicating a feature of pixel values of a block definedin the reference image data and a feature quantity indicating a featureof pixel values of a corresponding block in the comparison image data,is calculated by shifting a block having the same size as the block ofthe defined reference image data pixel by pixel in the horizontal linedirection (x direction). Then, based on the calculated correlationvalues, a matching process is performed to select a block of thecomparison image data having the highest correlation with the block ofthe reference image data from among the blocks in the comparison imagedata. Thereafter, the positional deviation between the target pixel ofthe block of the reference image data and the corresponding pixel of theblock of the comparison image data selected by the matching process iscalculated as a disparity value d. The parallax image data may beobtained by performing such a process of calculating a disparity value don the entire region or a specific region of the reference image data.

As a feature quantity of the block for the matching process, a value(luminance value) of each pixel within a block may be used, for example.As the correlation value, the sum of the absolute values of thedifference between the value (luminance value) of each of pixels in theblock of the reference image data and the value (luminance value) of acorresponding one of pixels in the block of the comparison image datamay be used, for example. In this case, the block having the smallestsum has the highest correlation.

For the matching process in the parallax image generation unit 11 to beimplemented by the hardware process, methods such as SSD (Sum of SquaredDifference), ZSSD (Zero-mean Sum of Squared Difference), SAD (Sum ofAbsolute Difference), ZSAD (Zero-mean Sum of Absolute Difference), NCC(Normalized cross correlation), and the like may be used. Note that inthe matching process, disparity values are calculated only on a pixelbasis; hence, when a disparity value of less than one pixel is required,it is necessary to use an estimated value. As an estimation method for adisparity value of less than one pixel, for example, an equiangularlinear fitting method, a curve fitting method or the like may be used.

<V-Map Generation Process>

The V-map generation unit 12 executes a V-map generation process forgenerating a V-map (a V-Disparity Map, an example of “vertical directiondistribution data”), based on parallax pixel data. Each parallax pixeldata included in the parallax image data is indicated by a set (x, y, d)of an x direction position, a y direction position, and a disparityvalue d. The parallax pixel data that is transformed intothree-dimensional coordinate information (d, y, f), where d is set onthe X axis, y is set on the Y axis, and frequency f is set on the Z axismay be generated as parallax histogram information. Or, threedimensional coordinate information (d, y, f) that is limited toinformation exceeding a predetermined frequency threshold value fromthis three-dimensional coordinate information (d, y, f) may be generatedas parallax histogram information. The parallax histogram information ofthe present embodiment includes three-dimensional coordinate information(d, y, f), and this three-dimensional histogram information distributedin the XY two-dimensional coordinate system is referred to as a V-map(V-disparity map).

More specifically, the V-map generation unit 12 calculates disparityvalue frequency distribution for each row region of the parallax imagedata obtained by dividing a parallax image into multiple parts in avertical direction. The information indicating the disparity valuefrequency distribution is parallax histogram information.

FIGS. 4A and 4B are diagrams illustrating parallax image data and aV-map generated from the parallax image data. FIG. 4A is a diagramillustrating an example of disparity value distribution of a parallaximage, and FIG. 4B is a diagram illustrating a V-map indicating thedisparity value frequency distribution by each row of the parallax imagein FIG. 4A.

When receiving an input of parallax image data having a disparity valuedistribution as illustrated in FIG. 4A, the V-map generation unit 12calculates a disparity value frequency distribution that is adistribution of the number of data sets for each disparity value perrow, and outputs the calculated disparity value frequency distributionas parallax histogram information. A V-map as illustrated in FIG. 4B maybe obtained by representing information on the disparity value frequencydistribution for each row obtained in this manner on a two-dimensionalorthogonal coordinate system, where a y-direction position (verticalposition of the captured image) on the parallax image is taken on theY-axis and the disparity value is taken on the X-axis. The V-map may beexpressed as an image in which pixels having pixel values according tothe frequency f are distributed on the two-dimensional orthogonalcoordinate system.

FIGS. 5A and 5B are diagrams illustrating an example of a captured imageas a reference image captured by one imaging part, and an example of aV-map corresponding to the captured image in FIG. 5A, respectively. Notethat FIG. 5A depicts the captured image, and FIG. 5B depicts the V-map.That is, the V-map illustrated in FIG. 5B is generated from the capturedimage as illustrated in FIG. 5A. In the V-map, no parallax is detectedin a region below the road surface, and the parallax is not counted in ashaded region A.

The example of an image in FIG. 5A depicts a road surface 401 on whichthe reference vehicle is traveling, a preceding vehicle 402 existingahead of the reference vehicle, and a utility pole 403 existing off theroad. The V-map in FIG. 5B depicts a road surface 501, a precedingvehicle 502, and a utility pole 503 corresponding to the example of theimage in FIG. 5A.

In the example of the image in FIG. 5A, a relatively flat road surfaceof the road surface ahead of the reference vehicle 100 matches a virtualreference road surface (virtual reference traveling surface). In otherwords, a road surface ahead of the reference vehicle 100, which extendsparallel to a road surface portion directly beneath the referencevehicle 100 toward a frontward direction of the reference vehicle,matches a virtual reference road surface (virtual reference travelingsurface). In this case, in a lower part of the V-map corresponding to alower part of the image, high frequency points (the road surface 501)are distributed in a substantially linear manner with the inclinationsuch that the disparity value d decreases toward the upper part of theimage. Pixels indicating such distribution are present at approximatelythe same distance in each row on the parallax image, have the highestoccupancy rate, and furthermore reflect a detection target having adistance becoming continuously farther toward the upper part of theimage.

The imaging part 510 a captures an image in a forward region of thereference vehicle, and content of the captured image indicates, asillustrated in FIG. 5B, that the disparity value d of the road surfacedecreases toward the upper part of the image in FIG. 5A. Further, thepixels displaying the road surface have substantially the same disparityvalue d within the same row (horizontal line). Accordingly, the highfrequency points (road surface 501) distributed in a substantiallylinear manner on the V-map correspond to the features of the pixels thatdisplay the road surface (vehicle traveling surface). Hence, pixels ofpoints distributed on or near an approximate straight line obtained bylinear approximation of high frequency points on the V-map may beestimated as pixels reflecting the road surface with high accuracy.Further, the distance to the road surface portion displayed in eachpixel may be obtained with high accuracy from the disparity value d ofthe corresponding point on the approximate straight line.

FIGS. 6A and B are diagrams illustrating an example of a captured imageas a reference image captured by one imaging part, and an example of aV-map of a predetermined region corresponding to the captured image,respectively.

The V-map generation unit 12 may generate a V-map using all the pixelsin the parallax image, or may generate a V-map using only pixels in apredetermined region (e.g., a region that may reflect a road surface) ina parallax image (an example of a captured image acting as a base of aparallax image in FIG. 6A). For example, the road surface becomesnarrower towards a vanishing point as a distance from the referencevehicle 100 increases; hence, as illustrated in FIG. 6A, a region may beset corresponding to the width of the road surface. As a result, it ispossible to prevent noise from being mixed in the V-map, where noise mayresult from an object (e.g., utility pole 403) located in a region otherthan the region that may reflect the road surface.

FIGS. 7A and 7B are diagrams illustrating an example of a captured imageas a reference image captured by one imaging part when noise isgenerated, and an example of a V-map corresponding to the capturedimage, respectively.

In the example of FIG. 7A, compared to the example of FIG. 6A, reflectedlight 404 from a puddle and the like and a disconnection 405 of a whiteline are depicted in FIG. 7A. The disconnection of the white lineoccurs, for example, when the white line disappears on an old (aging)road or when an interval between the white lines is long.

The V-map depicted in FIG. 7B includes noise generated by reflectedlight 504 from a puddle and the like, and a disconnection 505 of a whiteline. As depicted in FIG. 7B, pixels (parallax points) having afrequency value equal to or greater than a predetermined value (e.g., 1)are dispersed in a horizontal axis direction (direction of disparityvalue) by the reflected light 504 from the puddles or the like.

<Road Surface Estimation>

The road surface estimation unit 13 estimates (detects) a road surface,based on a parallax image generated by the parallax image generationunit 11. As depicted in FIG. 3, the road surface estimation unit 13includes a first road surface estimation unit 13 a, and a second roadsurface estimation unit 13 b. In the following description, the roadsurface estimation unit 13 estimates a road surface in two ways.However, the road surface estimation unit 13 may estimate a road surfaceby three or more ways.

The following illustrates an example of a functional configuration ofthe first road surface estimation unit 13 a with reference to FIG. 8.FIG. 8 is a functional block diagram illustrating an example of thefirst road surface estimation unit 13 a.

<First Road Surface Estimation>

The first road surface estimation unit 13 a includes a sample pointextraction unit 131, an outlier removal unit 132, a road surface shapedetection unit 133, a road surface complement unit 134, a smoothingprocess unit 135, a road surface determination unit 136, and a roadsurface height table calculation unit 15.

Hereinafter, a processing of each functional unit of the first roadsurface estimation unit 13 a will be described.

<<Sample Point Extraction Process>>

The sample point extraction unit 131 extracts sample points used forestimating a road surface from a V-map generated by the V-map generationunit 12.

The following describes examples in which the V-map is divided into aplurality of segments according to a disparity value (i.e., a distancevalue from the reference vehicle), and the sample point extractionprocess, the road surface shape detection process, and the likedescribed later are performed. However, the sample point extractionprocess, the road surface shape detection process, and the like may beperformed without dividing the V-map.

Next, a detailed example of the sample point extraction processperformed by the sample point extraction unit 131 will be described withreference to FIGS. 9 to 12. FIG. 9 is a flowchart illustrating anexample of the sample point extraction process.

First, the sample point extraction unit 131 divides a V-map into aplurality of segments according to disparity values corresponding to thehorizontal axis of the V-map (step S11).

Subsequently, the sample point extraction unit 131 sets a range (searchrange) for searching for a sample point to be extracted in a segment(first segment) having the largest disparity value (the closest distancefrom the reference vehicle) (step S12).

FIG. 10 is a diagram illustrating an example of a process of extractingsample points from a first segment.

For example, in the first segment, the sample point extraction unit 131determines, for example, a start point position 552 of a straight linecorresponding to a default road surface 551 (“preset road surface”) as areference point, and sets a predetermined range corresponding to thereference point as a sample point search region 553. The data on thedefault road surface is preset, for example, when a stereo camera isattached to the reference vehicle. For example, data on a flat roadsurface may be set.

For example, as illustrated in FIG. 10, the sample point extraction unit131 may determine a search region 553 to be an interval between twostraight lines 554 and 555 extending from the reference point acting asa start point to an adjacent segment at a predetermined angle. In thiscase, the sample point extraction unit 131 may determine the twostraight lines 554 and 555 in accordance with an angle at which the roadsurface is allowed to be inclined. For example, the sample pointextraction unit 131 may determine the lower straight line 554 withrespect to inclination of a downhill road surface that may be capturedby the stereo camera, and may determine the upper straight line 555 withrespect to the upper limit of inclination of an uphill road surfaceprescribed by law or the like. Alternatively, the sample pointextraction unit 131 may set the search region 553 to be, for example, arectangular region.

Subsequently, the sample point extraction unit 131 extracts a samplepoint from among pixels included in the search range (step S13). Thesample point extraction unit 131 may extract one or more sample pointsfrom among the pixels included in the search range, for example, foreach of coordinate positions of disparity values d. Alternatively, thesample point extraction unit 131 may extract the most frequentlyoccurring point indicating the highest frequency (mode) at a coordinateposition of each disparity value d as a sample point from among thepixels included in the search range. Or, the sample point extractionunit 131 may extract, from among the pixels included in the searchrange, the most frequently occurring point indicating the highestfrequency (mode) at a plurality of coordinate positions including adisparity value d (e.g., the coordinate position of each disparity valued and one or more coordinate positions of at least one of left or rightof the disparity value d) as a sample point.

Subsequently, the outlier removal unit 132, the road surface shapedetecting unit 133, and the road surface complement unit 134 detect aroad surface in the segment including the sample points, based on thesample points extracted in step S13 (step S14). Note that the roadsurface selected by the later-described road surface determination unit14 may be used as a road surface in the corresponding segment. Thus, forexample, in a case of the detected road surface being pulled upward dueto parallax of an object such as a preceding vehicle located on the roadsurface, a road surface in the next segment may be detected based on aroad surface detected by the second road surface estimation unit 13 b.

Subsequently, the sample point extraction unit 131 determines whetherthere is a next segment (e.g., a segment having the next smallestdisparity value) (step S15), and when there is no next segment (NO instep S15), the sample point extraction unit 131 ends the process.

When there is a next segment (YES in step S15), the sample pointextraction unit 131 acquires an end point position of the road surfacedetected in step S14 (step S16).

Subsequently, in the next segment, the sample point extraction unit 131sets a search range, based on the end point position of the road surfaceacquired in step S15 (step S17), and proceeds to a process in step S13.

FIGS. 11A and 11B are diagrams illustrating an example of a process ofextracting sample points from a second segment other than the firstsegment. For example, in the second segment, the sample point extractionunit 131 sets an end point position (a position at which the roadsurface 561 of the previous segment contacts the second segment) of theroad surface 561 of the previous segment (a segment adjacent to thesecond segment and from which the road surface has been alreadydetected) as a reference point 562. Then, as is the case of step S12illustrated in FIG. 10, the sample point extraction unit 131 sets apredetermined range corresponding to the reference point 562 as a samplepoint search region 563.

For example, as illustrated in FIG. 11A, the sample point extractionunit 131 may determine a search region 563 to be an interval between twostraight lines 564 and 565 extending from the reference point acting asa start point to an adjacent segment at a predetermined angle. In thiscase, the sample point extraction unit 131 may determine the twostraight lines 564 and 565 in accordance with an angle at which the roadsurface may be inclined. Alternatively, the sample point extraction unit131 may set the search region 563 to be a rectangular region having aheight corresponding to the y coordinate of the reference point 562, asillustrated in FIG. 11B.

Modification

FIG. 12 is a diagram illustrating another example of a process ofextracting sample points from the second segment.

For example, in the second segment, the sample point extraction unit 131sets an end point position of a road surface (history road surface) 561a of the segment adjacent to the second segment detected in a frame ofthe previous parallax image as a reference point 562 a. Then, the samplepoint extraction unit 131 sets a predetermined range corresponding tothe reference point 562 a as a sample point search region 563 a.

As a result, as illustrated in FIG. 12, in the case where a differencebetween the default road surface and the correct (actual) road surface566 is large, for example, on a road surface of a downward slope, a moreappropriate search range may be set compared with the case where the endpoint position of the road surface is set as the reference point asillustrated in FIGS. 11A and 11B.

Note that as the history road surface, the road surface detected in oneprevious frame may be used, or the average of the road surfaces detectedin the plurality of previous frames may be used.

<<Outlier Removal Process>>

The outlier removal unit 132 removes a sample point that is not suitablefor linear approximation from among the sample points extracted by thesample point extraction unit 131.

The following illustrates an outlier removal process performed by theoutlier removal unit 132 with reference to FIGS. 13 and 14. FIG. 13 is aflowchart illustrating an example of an outlier removal process. FIG. 14is a diagram illustrating a process of removing an outlier.

First, the outlier removal unit 132 calculates an approximate straightline from the sample points of each segment extracted by the samplepoint extraction unit 131 or from the sample points of all segments(step S20). The outlier removal unit 132 calculates an approximatestraight line using, for example, a least squares method. In the exampleof FIG. 14, the approximate straight line 541 is calculated in step S20in FIG. 13.

Subsequently, the outlier removal unit 132 calculates a threshold valueaccording to a value of an X coordinate (step S21). In the example ofFIG. 14, with a predetermined X coordinate value D (e.g., a disparityvalue corresponding to a distance of 50 m from the reference vehicle) asa boundary, a predetermined value 2σ is set to X coordinate values lessthan the predetermined X coordinate value D (a predetermined distancefarther from the reference vehicle), and a predetermined value a is setto X coordinate values having the predetermined X coordinate value D ormore (a predetermined distance or less from the reference vehicle). Thisis because the threshold for removing an outlier needs to be relaxedbecause an error generated when measuring with a stereo camera is largefor the road surface where the disparity values are small, that is, forthe distance from the reference vehicle being long.

Subsequently, the outlier removal unit 132 removes a sample point havingthe Euclidean distance being equal to or greater than the thresholdvalue calculated in step S21 with respect to the calculated approximatestraight line (step S22). In the example of FIG. 14, the sample point542 having an X coordinate value equal to or greater than D and beingseparated by a predetermined threshold a or more is removed.

<<Road Surface Shape Detection Process>>

The road surface shape detection unit 133 detects a shape (position,height) of the road surface from each segment of the V-map generated bythe V-map generation unit 12, based on the sample points extracted bythe sample point extraction unit 131 and not removed by the outlierremoval unit 132.

The road surface shape detection unit 133 calculates an approximatestraight line from the sample points of each segment, for example, by aleast squares method, and detects (estimates) the calculated approximatestraight line as a road surface.

<<Road Surface Complement Process>>

The road surface complement unit 134 determines whether the road surfacedetected (estimated) by the road surface shape detection unit 133 or theroad surface selected by the later-described road surface determinationunit 14 is inappropriate. When the road surface complement unit 134determines that the detected road surface or the selected road surfaceis inappropriate, the road surface complement unit 134 complements theroad surface.

The road surface complement unit 134 determines whether an inappropriateroad surface that is impossible to be captured by a stereo camera hasbeen estimated due to noise. When the road surface complement unit 134determines that an inappropriate road surface has been estimated, theroad surface complement unit 134 complements (interpolates) theinappropriate road surface, based on a default road surface or roadsurface data estimated in the previous frames.

In the V-map, for example, when data of a steeply left-sideupward-sloping road surface having part of the gradient being apredetermined value or more is detected, the road surface complementunit 134 assumes that the road surface is a downhill slope with a steepgradient as the distance from the reference vehicle increases. Then, theroad surface complement unit 134 removes the data of the road surfaceand complements the removed road surface data with data such as adefault road surface instead.

<<Smoothing Process>>

The smoothing process unit 135 corrects a road surface estimated in eachsegment such that the estimated road surfaces are continuous. Thesmoothing process unit 135 changes inclination and intercept of each ofthe road surfaces such that an end point (endpoint) of one of the roadsurfaces estimated in the two adjacent segments matches a start point(endpoint) of the other road surface.

<Second Road Surface Estimation>

The second road surface estimation unit 13 b estimates a road surface bya method differing from that of the first road surface estimation unit13 a.

With reference to FIG. 15, the road surface estimation process performedby the second road surface estimation unit 13 b will be described. FIG.15 is a diagram illustrating an example of a road surface estimationprocess performed by the second road surface estimation unit 13 b.

For example, in the sample point extraction process, the second roadsurface estimation unit 13 b extracts pixels representing the lowestheight, from among the pixels of the disparity points with respect tothe respective disparity values d in the V-map, as the sample points571A, . . . , 571N. The second road surface estimation unit 13 b thenextracts a second road surface 572 b, based on the extracted samplepoints, for example, by a process such as the above-described outlierremoval process. In this case, when the lowest point is noise, there isa possibility of estimating an erroneous road surface; hence, noise maybe removed by using the frequency of each coordinate.

In this case, the above method will not be affected by parallax of anobject existing on the road surface; hence, it is possible toappropriately detect a road surface, for example, in a case (scene) ofnot rainy weather (fine weather).

Note that the road surface estimation method by the first road surfaceestimation unit 13 a or the second road surface estimation unit 13 b isnot limited to the above-described example. For example, the roadsurface in a present frame may be used, for example, by averaging theplurality of road surfaces estimated based on a plurality of frames ofprevious parallax images. Alternatively, the road surface may beestimated by dividing a V-map into a plurality of segments and extendingthe road surface estimated by one segment to another segment, based onthe road surface estimated by the one segment, for example.Alternatively, instead of being approximated by a straight line, theroad surface may be approximated by a curve.

<Road Surface Determination Process>

The road surface determination unit 14 determines road surface data tobe employed, based on the road surface estimated by the first roadsurface estimation unit 13 a and the second road surface estimation unit13 b.

The road surface determination unit 14 selects one of the road surfaces,from among the respective road surfaces estimated by the first roadsurface estimation unit 13 a and the second road surface estimation unit13 b. Alternatively, the road surface determination unit 14 may performpredetermined weighting on the road surfaces estimated by the first roadsurface estimation unit 13 a and the second road surface estimation unit13 b, respectively, and combine the estimated road surfaces withpredetermined weights. For example, the road surface determination unit14 may set a value corresponding to the number of sample pointsextracted by each of the first road surface estimation unit 13 a and thesecond road surface estimation unit 13 b as a predetermined weightingvalue.

Next, with reference to FIGS. 16, 17A and 17B, a detailed example of aroad surface determination process by the road surface determinationunit 14 will be described. FIG. 16 is a flowchart illustrating anexample of the road surface determination process.

First, the road surface determination unit 14 acquires a road surface(first road surface) for each segment estimated from the first roadsurface estimation unit 13 a (step S31).

Subsequently, the road surface determination unit 14 acquires a roadsurface (second road surface) for each segment estimated from the secondroad surface estimation unit 13 b (step S32).

Subsequently, the road surface determination unit 14 calculatesinclination (gradient) of the first road surface and inclination of thesecond road surface in each segment (step S33).

Subsequently, the road surface determination unit 14 determines whetherthe difference between the inclination of the first road surface and theinclination of the second road surface in a target segment (any onesegment included in segments) is equal to or greater than apredetermined threshold value (Step S34).

When the difference between the inclination of the first road surfaceand the inclination of the second road surface is equal to or greaterthan the predetermined threshold value (YES in step S34), the roadsurface determination unit 14 selects one of the first road surface andthe second road surface that has the smaller inclination (step S35), andends the process.

When the difference between the inclination of the first road surfaceand the inclination of the second road surface is not equal to orgreater than the predetermined threshold value (NO in step S34), theroad surface determination unit 14 selects one of the first road surfaceand the second road surface that has the greater inclination (step S36),and ends the process.

FIGS. 17A and 17B are diagrams illustrating an example of the roadsurface determination process.

FIG. 17A is a diagram illustrating an example where the first roadsurface 572 a in a certain segment 573 estimated from the first roadsurface estimation unit 13 a is pulled upward by parallax of an objectsuch as a preceding vehicle positioned on the road surface.

In step S34 of FIG. 16, the road surface determination unit 14determines that the difference between the inclination of the first roadsurface and the inclination of the second road surface is equal to orgreater than the predetermined threshold value, in a case where thefollowing condition is satisfied.H1>A and H1/B>H2

In this condition, as illustrated in FIG. 17B, H1 represents thedifference between the Y coordinate of the end point of the first roadsurface 572 a and the Y coordinate of the end point of the second roadsurface 572 b in a certain segment 573. H2 represents the differencebetween the Y coordinate of the start point of the first road surface572 a and the Y coordinate of the start point of the second road surface572 b in the certain segment. A and B are predetermined constants.

In step S34 of FIG. 16, the road surface determination unit 14 may, forexample, determine that the first road surface is located above thesecond road surface, and the difference between the inclination of thefirst road surface and the inclination of the second road surface in thetarget segment is equal to or greater than a predetermined thresholdvalue.

Further, when the first road surface and the second road surface in thetarget segment cross each other, the road surface determination unit 14may select a road surface based, for example, on the upper and lower Ycoordinates of the end points in the target segment.

Effect of First Embodiment

When the inclination of the first road surface and the inclination ofthe second road surface in a certain segment are different, the firstroad surface described above may be pulled upward due to parallax of anobject such as a preceding vehicle positioned on the road surface. Or,the above-described second road surface may be pulled downward by thereflected light 504 from a puddle or the like as illustrated in FIG. 7B.

For example, it is assumed that for a first road surface, a pixel havinga value of greater frequency with respect to each disparity value d inthe V-map is extracted as a sample point, and for the second roadsurface, a pixel having a disparity value with the lowest Y coordinatewith respect to each disparity value d in the V-map is extracted as asample point. In such a case, according to the above-describedembodiment, the second road surface may be selected (adopted) when thefirst road surface is pulled upward by parallax of an object. Inaddition, when the second road surface is pulled downward due toreflected light from a puddle or the like, the first road surface may beselected.

Modification

According to the above-described first embodiment, the road surfacedetermination unit 14 selects a road surface to be employed, based onthe inclination of the first road surface and the inclination of thesecond road surface. Alternatively or additionally, the road surfacedetermination unit 14 selects a road surface to be employed, based onreliability (correlation coefficient) of each of the first road surfaceand the second road surface estimated by linear approximation. In thiscase, for example, when calculating the approximate straight line by theleast squares method based on the extracted sample points, the firstroad surface estimation unit 13 a and the second road surface estimationunit 13 b calculate a score based on the correlation coefficient betweenthe approximate straight line and each sample point. Then, the roadsurface determination unit 14 selects a road surface to be employed,according to the score of the first road surface and the score of thesecond road surface. When this modification is added to theabove-described road surface determination process, the processaccording to this modification may, for example, be performed, in placeof the process of step S36 in FIG. 16.

<Road Surface Height Table Calculation Process>

The road surface height table calculation unit 15 performs a roadsurface height table calculation process of calculating a road surfaceheight (a relative height with respect to the road surface portiondirectly beneath the reference vehicle), based on the road surface ineach segment corrected by the smoothing process unit 135, and convertingcalculated results into a table.

The road surface height table calculation unit 15 calculates a distanceto each road surface portion displayed in each row region (each positionin the vertical direction of an image) on the captured image frominformation on the road surface in each segment. It is predeterminedwhich row region in the captured image is to display each road surfaceportion in a vehicle traveling direction of a virtual plane, which isobtained by extending a road surface portion located directly beneaththe reference vehicle in a forward traveling direction of the referencevehicle in parallel with the road surface portion. This virtual plane(reference road surface) is represented by a straight line (referencestraight line) on the V-map. The road surface height table calculationunit 15 may obtain the height of each road surface portion ahead of thereference vehicle by comparing the road surface in each segment with thereference straight line. The road surface height table calculation unit15 may simply calculate the height of the road surface portion existingahead of the reference vehicle by the distance from the Y axis positionon the road surface in each segment obtained from the correspondingdisparity value. The road surface height table calculation unit 15tabulates the height of each road surface portion obtained from theapproximate straight line with respect to the necessary disparity range.

Note that the height of an object displayed on the captured imageportion corresponding to a certain point where the Y axis position is y′at a disparity value d from the road surface may be calculated from(y′−y0) when the Y-axis position on the road surface at the disparityvalue d is y0. In general, the height H of the object corresponding tothe coordinates (d, y′) on the V-map from the road surface may becalculated from the following formula. Note that “Z” in the followingformula is a distance (Z=BF/(d-offset)) calculated from the disparityvalue d, and “f” is a value obtained by converting a focal distance of acamera into the same unit as that of (y′−Y0). Note that “BF” is a valueobtained by multiplying the baseline length of a stereo camera by thefocal length, and “offset” is a disparity value when an object atinfinity is imaged.H=z×(y′−y0)/f<Clustering, Rejection, Tracking>

A clustering unit 16 generates XY two-dimensional histogram information(frequency U-map) by setting a set (x, y, d) of x being an x directionposition, y being a y direction position, and d being a disparity valued in each parallax pixel data included in the parallax image data, suchthat x is set on the X axis, d is set on the Y axis, and the frequencyis set on the Z axis.

The clustering unit 16 generates a frequency U-map only for the points(x, y, d) of the parallax image in which the height H from the roadsurface is within a predetermined height range (e.g., 20 cm to 3 m),based on the height of each road surface portion tabulated by the roadsurface height table calculation unit 15. In this case, it is possibleto appropriately extract an object existing in the predetermined heightrange from the road surface.

In the frequency U-map, the clustering unit 16 detects, as an objectregion, a region where the frequency is greater than a predeterminedvalue and the parallax is dense, and assigns, to the object region,individual information, such as coordinates on the parallax image and atype (human or pedestrian) of an object predicted from the actual size(size) of the object.

The rejection unit 17 rejects information on an object that is not arecognition target based on the parallax image, the frequency U-map, andthe individual information of the object.

A tracking unit 18 determines whether the detected object is a trackingtarget when the detected object appears consecutively in frames of aplurality of parallax images.

<Traveling Support Control>

A control unit 19 may, for example, send an alert sign to a driver ofthe reference vehicle 100 or perform traveling support control (drivingsupport control) such as control of the steering wheel and braking ofthe reference vehicle, based on the detection result of the object bythe clustering unit 16.

Second Embodiment

According to the first embodiment, the road surface determination unit14 selects a road surface to be employed based on the inclination of thefirst road surface and the inclination of the second road surface. Inthe second embodiment, the road surface determination unit 14 selects aroad surface to be employed, based on a distribution shape or the numberof the disparity points in a predetermined region including the firstroad surface and the second road surface. Note that since the secondembodiment is the same as the first embodiment except a part thereof, aduplicated illustration is appropriately omitted.

The following illustrates details of a process of the in-vehicle devicecontrol system 1 according to the second embodiment with respect to thedifference from the first embodiment.

A detailed example of a road surface determination process performed bythe road surface determination unit 14 according to the secondembodiment will be described, with reference to FIGS. 18 and 19. FIG. 18is an example of a flowchart illustrating the road surface determinationprocess according to the second embodiment. FIGS. 19A and 19B arediagrams each illustrating an example of a region such as a rectangleincluding the first road surface and the second road surface.

First, as illustrated in FIG. 18, the road surface determination unit 14sets a region such as a rectangle including the first road surfaceestimated by the first road surface estimation unit 13 a, and the secondroad surface estimated by the second road surface estimation unit 13 b(step S201).

Subsequently, the road surface determination unit 14 calculates thenumber of disparity points included in the set region (step S202).

Subsequently, the road surface determination unit 14 calculates thedensity of the disparity points in the set region (step S203). Forexample, the road surface determination unit 14 calculates the densityby dividing the disparity points in the set region by the area of theset region.

Subsequently, the road surface determination unit 14 determines whetherthe density of the disparity points in the set region is equal to orgreater than a predetermined threshold value (step S204). Note thatalternatively, whether the set region is equal to or greater than apredetermined threshold value may be determined by using the number ofdisparity points when the area of a region to be set is constant.

When the density of the disparity points in the set region is equal toor greater than the predetermined threshold value (YES in step S204),the second road surface 581 a existing in a lower part in height in avertical direction may possibly be affected by noise due to a puddle inrainy weather, as illustrated in FIG. 19A. Accordingly, the road surfacedetermination unit 14 selects the first road surface 582 a existing inan upper part in height in a vertical direction (step S205), and endsthe process.

When the density of the disparity points in the set region is not equalto or greater than the predetermined threshold value (NO in step S204),the road surface determination unit 14 acquires a distribution shape ofthe disparity points included in the set region (step S206).

Subsequently, the road surface determination unit 14 determines whetherthe distribution shape of the disparity points included in the setregion is a predetermined shape (step S207). Note that the predeterminedshape may be determined to have a distribution of disparity points of atleast one of an upper right 583 portion and a lower left 584 portionwithin the set region that is equal to or less than a predeterminedvalue. In this case, when the density of or the number of disparitypoints of at least one of the upper right 583 portion and the lower left584 portion within the set region is equal to or less than thepredetermined value, the road surface determination unit 14 determinesthat the distribution shape of the disparity points in the set region isthe predetermined shape.

When the distribution shape of the disparity points included in the setregion is the predetermined shape (YES in step S207), the first roadsurface 582 b existing in the upper part may possibly be pulled upwarddue to parallax of the object, as illustrated in FIG. 19B. Accordingly,the road surface determination unit 14 selects the second road surface581 b existing in the lower part (step S208), and ends the process.

When the distribution shape of the disparity points included in the setregion is not the predetermined shape (NO in step S207), the roadsurface determination unit 14 selects the first road surface in the samemanner as in step S205, and ends the process. Alternatively, the roadsurface determination unit 14 may perform the road surface determinationprocess in the first embodiment to select a road surface.

Effect of Second Embodiment

According to the second embodiment, advantageous effects similar tothose of the first embodiment may be obtained.

Third Embodiment

According to the third embodiment, the road surface determination unit14 performs image recognition within a predetermined region of acaptured image (luminance image) or a parallax image, and selects a roadsurface to be employed, based on the result of the image recognition.Note that since the third embodiment is the same as the first embodimentexcept a part thereof, a duplicated illustration is appropriatelyomitted.

The following illustrates details of a process of the in-vehicle devicecontrol system 1 according to the third embodiment with respect to thedifference from the first embodiment.

A detailed example of a road surface determination process performed bythe road surface determination unit 14 according to the third embodimentwill be described, with reference to FIGS. 20 and 21. FIG. 20 is anexample of a flowchart illustrating the road surface determinationprocess according to the third embodiment.

First, the road surface determination unit 14 sets respective segmentsin a region that may possibly reflect a road surface, of a capturedimage or a parallax image (step S301). FIG. 21 is a diagram illustratinga correspondence relationship between a captured image or a parallaximage, and a V-map. FIG. 21 is a diagram illustrating a case where aregion that may possibly reflect a road surface is divided into threesegments 591, 592, and 593.

Subsequently, the road surface determination unit 14 performs imagerecognition on respective segments of the captured image or the parallaximage (step S302).

Note that any given method may be used as the image recognition methodin step S302. For example, a template for an object such as a vehicle, aperson, a road surface, raindrops or the like may be prepared inadvance, and such an object may be recognized by template matching.

Further, the Bag-of-Visual-Words method may be used for recognition maybe used; the Bag-of-Visual-Words uses a vector called visual wordsquantized local features such as Scale-Invariant Feature Transform(SIFT) as described in “Csurka, G., Bray, C., Dance, C. and Fan, L,“Visual categorization with bags of keypoints,” Proc. ECCV Workshop onStatistical Learning in Computer Vision, pp. 1-22, 2004.”.Alternatively, a method using Deep Learning with multilayered neuralnetworks may be used, which is described, for example, in “AlexKrizhevsky, Ilya Sutskever, and Geoffrey E Hinton., “Imagenetclassification with deep convolutional neural networks,” In Advances inneural information processing systems, pp. 1097-1105, 2012.”.

Further, when image recognition is performed, each segment may bedivided and a sequential recognition process may be performed on thedivided segments while raster scan is performed. In this case, since aregion including noise may be removed, recognition accuracy may beimproved, compared to a case subjecting the entire segment torecognition processing.

Subsequently, the road surface determination unit 14 determines whetherit is rainy (rainy scene), based on the image recognition result of stepS302 (step S303).

When the image recognition result indicates rainy weather (rainy scene)(YES in step S303), the second road surface existing in a lower part maybe affected by noise due to a puddle in rainy weather. Accordingly, theroad surface determination unit 14 selects the first road surfaceexisting in the upper part (step S304), and ends the process.

When the image recognition result does not indicate rainy weather (NO instep S303), the road surface determination unit 14 determines whether animage of an object such as a preceding vehicle (594 in FIG. 21) isrecognized in each segment (step S305).

When an image of an object such as a preceding vehicle is recognized(YES in step S305), the first road surface existing in the upper partmay possibly be pulled upward by parallax (594 a in FIG. 21) of anobject. Accordingly, the road surface determination unit 14 selects thesecond road surface 581 b existing in the lower part of the segmentrecognizing the image of the object such as the preceding vehicle (stepS306), and ends the process.

When the image of the object such as the preceding vehicle is notrecognized (NO in step S305), the road surface determination unit 14may, for example, select the first road surface in the same manner as instep S204, and ends the process. Alternatively, the road surfacedetermination unit 14 may perform the road surface determination processin each of the above-described embodiments to select a road surface.

Overview

When noise is generated in parallax due to reflection of the roadsurface during rainy weather, an estimated road surface may be too lowor too high with respect to the correct road surface. When the estimatedroad surface is too low, a part of the road surface may be erroneouslyrecognized as an obstacle. When the estimated road surface is too high,an obstacle or the like lower than the estimated road surface will notbe detected in some cases.

According to each of the above-described embodiments, a plurality ofroad surfaces are estimated, based on the V-map, and a road surface isdetermined based on the plurality of estimated road surfaces. This makesit possible to improve the accuracy of detecting a road surface.

Note that since a value of a distance (distance value) and a disparityvalue may be handled equivalently, a parallax image is used as anexample of a range image in the present embodiments; however, thepresent invention is not limited to this example. For example, a rangeimage may be generated by integrating distance information generated byusing a detection device such as millimeter wave radar or laser radarwith respect to a parallax image generated by using a stereo camera.Further, a combination of a stereo camera and a detection device such asmillimeter wave radar or laser radar may combine a detection result ofan object obtained by the detection device with the detection result ofthe object obtained by the above-described stereo camera to furtherimprove detection accuracy.

The system configuration in the above-described embodiments is merely anexample, and various examples of the system configuration may also beapplied according to intended use and purposes. In addition, it is alsopossible to combine some or all of the above-described embodiments.

For example, because the processes of the outlier removal unit 132, theroad surface complement unit 134, the smoothing process unit 135 and thelike are not indispensable, the system configuration may exclude thesefunctional units.

In addition, respective functional units of the process hardware unit510, the image analysis unit 600, and the vehicle traveling control unit104 may be implemented by hardware, or may be implemented by a CPUexecuting a program stored in a storage device. The above-describedprogram may be distributed in a form of a computer-readable recordingmedium storing the program in files of an installable format orexecutable format. Alternatively, other examples of the recording mediummay include a compact disc recordable (CD-R), a digital versatile disk(DVD), and a Blu-ray Disc. The above-described recording media thatstore the above-described programs such as a CD-ROM, and a HD 504 thatstore these programs may be provided domestically or internationally asa program product.

Advantage of the Invention

According to the disclosed technique, it is possible to improve theaccuracy of detecting a road surface.

Although the present invention has been described based on theembodiments, the present invention is not limited to the above-describedembodiments, and various modifications may be made within the scopedescribed in the claims.

What is claimed is:
 1. An image processing apparatus, comprising:processing circuitry configured to: generate vertical directiondistribution data indicating a frequency distribution of distance valueswith respect to a vertical direction of a range image, from the rangeimage having distance values according to distance of a road surface ina plurality of captured images captured by a plurality of imaging parts;estimate a plurality of road surfaces, based on the vertical directiondistribution data; and determine a desired road surface, from among theestimated plurality of road surfaces, wherein the processing circuitryis further configured to, in determining the desired road surface,determine, as the desired road surface, a particular road surface havinga smallest inclination, when a difference between the inclinations ofthe estimated plurality of road surfaces is equal to or greater than apredetermined threshold value.
 2. The image processing apparatusaccording to claim 1, wherein the processing circuitry is furtherconfigured to, in estimating the plurality of road surfaces, estimatethe plurality of road surfaces by a linear approximation using a leastsquares method, based on the vertical direction distribution data, andwherein, in determining the desired road surface, the processingcircuitry is further configured to determine the desired road surfacebased on a correlation coefficient of each road surface, of theestimated plurality of road surfaces, upon the performed linearapproximation.
 3. The image processing apparatus according to claim 1,wherein the processing circuitry is further configured to, indetermining the desired road surface, determine, as the desired roadsurface, a road surface that is highest in height, when a number of or adensity of pixels in a predetermined region is equal to or greater thana predetermined threshold value, the pixels having a distance valueequal to or greater than a predetermined value, and the predeterminedregion including each of the estimated plurality of road surfaces. 4.The image processing apparatus according to claim 1, wherein theprocessing circuitry is further configured to, in determining thedesired road surface, determine, as the desired road surface, aparticular road surface that is lowest in height, when a distributionshape of pixels in a predetermined region indicating a distribution ofpixels of one of a first portion and a second portion is equal to orless than a predetermined value, the first portion has a large parallaxand is higher in height and the second portion has a small parallax andis lower in height, the pixels have a distance value equal to or greaterthan a predetermined value, and the predetermined region includes eachof the estimated plurality of road surfaces.
 5. The image processingapparatus according to claim 1, wherein the processing circuitry isfurther configured to, in determining the desired road surface, performimage recognition on one of the range image and one of the capturedimages, and determine, as the desired road surface, a particular roadsurface that is lowest in height, when recognizing an object other thanthe particular road surface.
 6. The image processing apparatus accordingto claim 1, wherein the processing circuitry is further configured to,in determining the desired road surface, perform image recognition onone of the range image and one of the captured images, and determine, asthe desired road surface, a particular road surface that is highest inheight, when recognizing raindrops.
 7. The image processing apparatusaccording to claim 1, wherein the processing circuitry is furtherconfigured to, in estimating the plurality of road surfaces, estimatethe plurality of road surfaces with respect to a predetermined regioncorresponding to a predetermined distance value of the verticaldirection distribution data, and wherein the processing circuitry isfurther configured to, in determining the desired road surface,determine, as the desired road surface, a particular road surface to beemployed in the predetermined region, from the estimated plurality ofroad surfaces.
 8. The image processing apparatus according to claim 1,wherein the processing circuitry is further configured to, in estimatingthe plurality of road surfaces, divide the vertical directiondistribution data into a plurality of regions according to distancevalues, and estimate the plurality of road surfaces with respect to apredetermined region selected from among the plurality of dividedregions, and wherein the processing circuitry is further configured to,in determining the desired road surface, determine, as the desired roadsurface, a particular road surface to be employed in the predeterminedregion, from among the estimated plurality of road surfaces.
 9. Theimage processing apparatus according to claim 1, wherein the processingcircuitry is further configured to, in estimating the plurality of roadsurfaces, divide the vertical direction distribution data into aplurality of regions according to distance values, and estimate a firstroad surface and a second road surface with respect to a predeterminedregion among the plurality of divided regions, and wherein theprocessing circuitry is further configured to, in determining thedesired road surface, determine one of the first road surface and thesecond road surface that has a smaller inclination as a road surface tobe employed in the predetermined region, to when H1>A and H1/B>H2 issatisfied, wherein H1 represents a difference between a verticalposition of an end point of the first road surface and a verticalposition of an end point of the second road surface in the predeterminedregion, H2 represents a difference between a vertical position of astart point of the first road surface and a vertical position of a startpoint of the second road surface in the predetermined region, Arepresents a predetermined first constant, and B represents apredetermined second constant.
 10. The image processing apparatusaccording to claim 1, further comprising an imaging device including:the plurality of imaging parts, which are configured to capture animage; and the processing circuitry, which is configured to: generatethe range image having the distance values according to parallax of anobject in the plurality of captured images, from the plurality ofcaptured images captured by the plurality of imaging parts; generate thevertical direction distribution data indicating the frequencydistribution of distance values with respect to the vertical directionof the range image; estimate the plurality of road surfaces, based onthe vertical direction distribution data; and determine the desired roadsurface, based on the estimated plurality of road surfaces.
 11. Theimage processing apparatus of claim 1, wherein the processing circuitryis further configured to determine, as the desired road surface, aparticular road surface having a largest inclination, when a differencebetween the inclinations of the estimated plurality of road surfaces isless than a predetermined threshold value.
 12. A moving body devicecontrol system, comprising: a plurality of imaging parts installed in amoving body and configured to image a view ahead of the moving body; andprocessing circuitry configured to: generate a range image havingdistance values according to parallax of objects in a plurality ofcaptured images, from the plurality of captured images captured by theplurality of imaging parts; generate vertical direction distributiondata indicating a frequency distribution of distance values with respectto a vertical direction of the range image; estimate a plurality ofsurfaces, based on the vertical direction distribution data; determine adesired surface, from among the plurality of estimated surfaces; detecta particular object in the plurality of captured images, based on thedetermined surface and the range image; and control the moving body,based on data of the detected object, wherein the processing circuitryis further configured to, in determining the desired road surface,determine, as the desired road surface, a particular road surface havinga smallest inclination, when a difference between the inclinations ofthe estimated plurality of road surfaces is equal to or greater than apredetermined threshold value.
 13. A moving body, comprising: the movingbody device control system according to claim 12, wherein the movingbody is controlled by the moving control device control system.
 14. Anon-transitory computer readable medium storing instructions which, whenexecuted by a computer, cause the computer to: generate verticaldirection distribution data indicating a frequency distribution ofdistance values with respect to a vertical direction of a range image,from the range image having distance values according to distance of aroad surface in a plurality of captured images captured by a pluralityof imaging parts; estimate a plurality of road surfaces, based on thevertical direction distribution data; and determine a desired roadsurface, from among the plurality of estimated road surfaces, whereinthe determining step further comprises determining, as the desired roadsurface, a particular road surface having a smallest inclination, when adifference between the inclinations of the estimated plurality of roadsurfaces is equal to or greater than a predetermined threshold value.